1. Field of the Invention
The invention relates to a method of fabricating a composite insulator having a protective housing made of polymer materials incorporating an antiozonant and an antioxidant.
2. Discussion of the Background Art
The housing of electric insulators made of composite materials and used either as line insulators or substation insulators, or else for other electrical equipment, is generally made of polymer or elastomer materials such as silicone, ethylene propylene diene monomer (EPDM), ethylene propylene monomer (EPM), or other suitable materials. To simplify, these polymer or elastomer materials are referred to below as “polymer material”.
Such an insulator is used in electricity networks or in high voltage equipment. It is more particularly intended for installing in the open end where it is subjected to attack from the surroundings. Under certain environmental conditions, the surface of the polymer material housing changes and affects the performance of the insulator.
Analyses performed firstly on insulators taken from lines, and secondly in the laboratory on samples of polymer materials subjected to electric activity, show that this change is caused by the surface of the polymer material housing being attacked by ozone and by nitric acid.
This change to the surface of the housing is a direct consequence of the electrical activity of the surface under outdoor conditions that favor such change: the ozone is generated by electric discharge into the surrounding air, and the ozone reacting with the nitrogen, the oxygen, and the moisture of the air lead to nitric acid being formed.
Document WO 91/06106 presents a composite insulator that may be covered in a housing for protecting it against the effects of the surroundings, including ozone attack.
Document U.S. Pat. No. 4,638,026 discloses stabilizing polymer materials by using antioxidant agents from the family of of phenolic antioxidants and antiozonant agents from the family of phenylenediamines. Such agents may be used for example in the automobile field for protecting the material constituting tires.
In the field of composite material electric insulators, document US 2005/0209384 discloses a method of treating an electric insulator by covering its surface with a silicone elastomer housing in order to protect it from the outside environment. Nevertheless, no specific mention is made of providing anti-ozone protection for the surface of the housing.